Well known torque sensing tools and devices have provided a wide variety of means for either measuring torque or for permitting slippage of a supporting tool when a predetermined torque is exceeded. Included among such means, and most commonly found in the torque measuring art, has been the use of elongated torsion bars or rods for operatively connecting a wrench or the like and a socket or similar workpiece. Since torsion bars for this purpose have been selected according to their particular modulus of elasticity, torque measurement has generally been achieved by variously coupling a pointer or indicator to one extremity of a torsion bar and a calibrated scale to the other extremity thereof, the pointer being displaced from its normal "zero" reading as the torsion bar flexes or twists. Typical of the torque measuring art involving the use of torsion bars or rods are U.S. Pat. Nos. 3,911,736 to Miller, 3,691,826 to Grabovac, 3,481,193 to Schubert and 2,934,946 to Engquist. Although generally suitable for torque measuring per se, these torsion bar devices have generally been of an intricate nature entailing relatively high manufacturing costs, and have further been limited in use to those applications where space limitations have not been critical, as where a ratchet wrench or the like may be operated at a sufficient distance from the socket to accommodate the elongated bar.
Also found in the torque measuring art are various devices making use of torsion or helical springs, such as U.S. Pat. Nos. 2,151,953 to Zimmerman and 2,250,736 to Torresen; and making use of tension springs such as U.S. Pat. No. 1,574,491 to Leake. These torsion springs and tension springs have been characterized by some means of end-anchoring, thereby permitting torque measurement in one direction only.
An additional common characteristic of known torsion bar and spring, and tension spring torque measuring devices is that they are designed for measurement in predetermined set torque ranges only, and lack the flexibility of being readily adaptable to accommodate widely differing ranges of torque.